Single domain to vortex state transition in multilayered cobalt/copper nanowires

Multilayered magnetic nanowires provide ideal platforms for nanomagnetism and spin-transport studies. They exhibit complex magnetization reversal behaviors as dimensions of the magnetic components are varied, which are difficult to probe since the magnetic entities are buried inside the nanowires. We have captured magnetic and magnetoresistance "fingerprints" of Co nanodiscs in Co/Cu multilayered nanowires as they undergo a single domain to vortex state transition, using a first-order reversal curve (FORC) method. The Co/Cu multilayered nanowires have been synthesized by pulsed electrodeposition into nanoporous polycarbonate membranes. In 50 nm diameter nanowires of [Co(5nm)/Cu(8nm)]400, a 10% magnetoresistance effect is observed at 300 K. In 200 nm diameter nanowires, the magnetic configurations can be tuned by adjusting the Co nanodisc aspect ratio. The thinnest nanodiscs exhibit single domain behavior. The thicker ones exhibit vortex states, where the nucleation and annihilation of the vortices are manifested as butterfly-like features in the FORC distributions. The magnetoresistance effect shows different characteristics, which correspond to the different magnetic configurations of the Co nanodiscs.

[1]  Matthew R. Gibbons,et al.  Magnetic domain structure and magnetization reversal in submicron-scale Co dots , 1998 .

[2]  F Pázmándi,et al.  Reversal-field memory in the hysteresis of spin glasses. , 2002, Physical review letters.

[3]  T. Devolder,et al.  Planar patterned magnetic media obtained by ion irradiation , 1998, Science.

[4]  I. Schuller,et al.  Magnetic fingerprints of sub-100 nm Fe dots , 2007, 0704.0127.

[5]  Sun,et al.  Monodisperse FePt nanoparticles and ferromagnetic FePt nanocrystal superlattices , 2000, Science.

[6]  Thermal fluctuation effects on quasistatic magnetic switching of patterned Ni81Fe19 elements (invited) , 2002 .

[7]  Ono,et al.  Magnetic vortex core observation in circular dots of permalloy , 2000, Science.

[8]  Russell P. Cowburn,et al.  Micromagnetics Simulation of Deep-Submicron Supermalloy Disks , 2001 .

[9]  Peter Vettiger,et al.  Ion-beam patterning of magnetic films using stencil masks , 1999 .

[10]  A. Romero,et al.  Vortex state and effect of anisotropy in sub-100-nm magnetic nanodots , 2006 .

[11]  V. Rose,et al.  The breakdown of the fingerprinting of vortices by hysteresis loops in circular multilayer ring arrays , 2007 .

[12]  V. Novosad,et al.  Imprinting vortices into antiferromagnets. , 2006, Physical review letters.

[13]  Dongqi Li,et al.  Magnetic bistability of Co nanodots. , 2005, Physical review letters.

[14]  C. Ross.  Patterned Magnetic Recording Media , 2001 .

[15]  C. R. Pike,et al.  An investigation of magnetic reversal in submicron-scale Co dots using first order reversal curve diagrams , 1999 .

[16]  I. Schuller,et al.  Ordered magnetic nanostructures: fabrication and properties , 2003 .

[17]  Andrew P. Roberts,et al.  Characterizing interactions in fine magnetic particle systems using first order reversal curves , 1999 .

[18]  R. Wiesendanger,et al.  Direct Observation of Internal Spin Structure of Magnetic Vortex Cores , 2002, Science.

[19]  I. Schuller,et al.  Irreversibility of magnetization rotation in exchange biased Fe/epitaxial-FeF2 thin films , 2007 .

[20]  Chien,et al.  Perpendicular giant magnetoresistance of multilayered Co/Cu nanowires. , 1995, Physical review. B, Condensed matter.

[21]  R. Cowburn,et al.  Single-Domain Circular Nanomagnets , 1999 .

[22]  Valentyn Novosad,et al.  Magnetization reversal due to vortex nucleation, displacement, and annihilation in submicron ferromagnetic dot arrays , 2001 .

[23]  I. Schuller,et al.  Temperature induced single domain-vortex state transition in sub-100 nm Fe nanodots , 2007 .

[24]  O. Hellwig,et al.  Magnetization reversal of Co/Pt multilayers: Microscopic origin of high-field magnetic irreversibility - eScholarship , 2004 .

[25]  Etienne,et al.  Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. , 1988, Physical review letters.

[26]  G. Rowlands,et al.  Energetics of magnetic ring and disk elements: Uniform versus vortex state , 2006 .

[27]  Albert Fert,et al.  Giant magnetoresistance in magnetic multilayered nanowires , 1994 .

[28]  J. Ansermet,et al.  Giant magnetoresistance of nanowires of multilayers , 1994 .

[29]  H. Hoffmann,et al.  Single domain and vortex state in ferromagnetic circular nanodots , 2002 .

[30]  J. Zhu,et al.  Ultrahigh‐Density Arrays of Ferromagnetic Nanorings on Macroscopic Areas , 2004 .

[31]  C. Chien,et al.  Fabrication and Magnetic Properties of Arrays of Metallic Nanowires , 1993, Science.

[32]  Binasch,et al.  Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange. , 1989, Physical review. B, Condensed matter.